U.S. patent number 6,411,353 [Application Number 09/294,346] was granted by the patent office on 2002-06-25 for liquid crystal display device with its upper and lower cases clamped by crimping portions thereof.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Kaoru Hasegawa, Kengo Kobayashi, Yoshio Toriyama, Katsuhiko Yarita.
United States Patent |
6,411,353 |
Yarita , et al. |
June 25, 2002 |
Liquid crystal display device with its upper and lower cases
clamped by crimping portions thereof
Abstract
A liquid crystal display device includes a liquid crystal
display element having a liquid crystal layer sandwiched between a
pair of upper and lower substrates, a flexible circuit board
disposed around a periphery of the liquid crystal display element,
an illuminating light source having a line light source, a light
guide and a reflector and disposed behind the liquid crystal
display element, a metal upper case having a sidewall bent back and
a display window, a resin lower case for housing the illuminating
light source. The upper and lower cases are clamped by crimping
plural nails formed in the sidewall of the upper case at an outer
surface of the lower case after stacking the liquid crystal display
element, the flexible circuit board and the illuminating light
source between the upper and lower cases. An electrical connection
between the upper case and a grounding pattern formed on the
flexible circuit board is made by at least one component in chip
form having a conductive region and being attached to a portion of
the grounding pattern bent over the lower substrate, and a metal
tape having one end thereof being interposed between opposing
portions of the upper and lower cases which are pressed against
each other and the other end thereof being positioned to be pressed
against the conductive region of the at least one component.
Inventors: |
Yarita; Katsuhiko (Mobara,
JP), Hasegawa; Kaoru (Chosei-gun, JP),
Kobayashi; Kengo (Mobara, JP), Toriyama; Yoshio
(Chosei-gun, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
14570940 |
Appl.
No.: |
09/294,346 |
Filed: |
April 20, 1999 |
Foreign Application Priority Data
|
|
|
|
|
Apr 22, 1998 [JP] |
|
|
10-111818 |
|
Current U.S.
Class: |
349/59; 349/150;
349/58 |
Current CPC
Class: |
G02F
1/133308 (20130101); G02F 1/13452 (20130101); G06F
1/1637 (20130101); G02F 2201/503 (20130101); G02F
2201/465 (20130101) |
Current International
Class: |
G02F
1/13 (20060101); G02F 001/133 (); G02F
001/134 () |
Field of
Search: |
;349/58,62,63,67,150,46,59,61 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sikes; William L.
Assistant Examiner: Nguyen; Hoan
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus, LLP
Claims
What is claimed is:
1. A liquid crystal display device comprising:
a liquid crystal display element having a liquid crystal layer
sandwiched between a pair of upper and lower substrates,
a flexible circuit board disposed around a periphery of a lower of
said lower substrate,
an illuminating light source under said liquid crystal display
element,
an upper case made of metal, having an upper portion provided with
a window corresponding to a useful display area of said liquid
crystal display element and a sidewall bent from a periphery of the
upper portion thereof,
a lower case made of resin for housing said illuminating light
source,
said upper case and said lower case being clamped by crimping a
plurality of nails formed in said sidewall of said upper case at an
outer surface of said lower case and having said liquid crystal
display element and said flexible circuit board being disposed
therebetween,
wherein an electrical connection between said upper case and a
grounding pattern formed on said flexible circuit board is made by
at least one component in chip form having a conductive region and
being attached to a portion of said grounding pattern bent over
said lower substrate, and a metal tape having one end thereof being
interposed between opposing portions of said upper and lower cases
and an other end thereof being positioned on an upper side of said
lower case to be pressed against said conductive region of said at
least one component in chip form.
2. A liquid crystal display device according to claim 1, wherein
said lower case is provided with a recess for housing each of said
at least one component in chip form at said upper side thereof, and
a sheet of elastic material interposed between said metal tape and
a bottom of said recess.
3. A liquid crystal display device according to claim 1, wherein
said at least one component in chip form comprises a ceramic
substrate and a metallized film formed on said ceramic
substrate.
4. A liquid crystal display device according to claim 1, wherein
said at least one component in chip form is a chip capacitor.
5. A liquid crystal display device according to claim 1, wherein
said at least one component in chip form is a chip resistor.
6. A liquid crystal display device according to claim 1, wherein
said at least one component in chip form is 2 mm at most in length,
width and thickness.
7. A liquid crystal display device according to claim 1, wherein
said at least one component in chip form is a sheet made of
metal.
8. A liquid crystal display device comprising:
a liquid crystal display element having a liquid crystal layer
sandwiched between a pair of upper and lower substrates,
an illuminating light source comprising a line light source, a
light guide and a reflector and disposed under said liquid crystal
display element,
an upper case made of metal, having an upper portion provided with
a window corresponding to a useful display area of said liquid
crystal display element and a sidewall bent down from a periphery
of the upper portion thereof,
a lower case made of resin for housing said illuminating light
source and having a peripheral frame portion for supporting said
light guide,
said upper case and said lower case being clamped by crimping a
plurality of nails formed in said sidewall of said upper case at an
outer surface of said lower case and having said liquid crystal
display element and said flexible circuit board being disposed
therebetween,
wherein a rubber cushion is disposed between a lower side of said
light guide and peripheral portions of said lower case at least in
the vicinity of portions where said upper case and said lower case
are clamped by crimping said plurality of nails.
9. A liquid crystal display device comprising:
a liquid crystal display element having a liquid crystal layer
sandwiched between a pair of upper and lower substrates,
an illuminating light source under said liquid crystal display
element,
an upper case made of metal, having an upper portion provided with
a window corresponding to a useful display area of said liquid
crystal display element and a sidewall bent down from a periphery
of the upper portion thereof,
a lower case made of resin for housing said illuminating light
source,
said upper case and said lower case being clamped by crimping a
plurality of nails formed in said sidewall of said upper case at an
outer surface of said lower case and having said liquid crystal
display element and said flexible circuit board disposed
therebetween,
wherein each of said plurality of nails is crimped in a plane
parallel with an underside of said lower case and has at least one
bend before being crimped in cross section parallel to said plane.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device
(hereinafter, referred to as "LCD"), and particularly to an LCD
with its upper and lower cases clamped together by crimping
portions of one of the upper and lower cases at the other.
LCDs have been widely adopted as display devices capable of
displaying a high-definition color image used for notebook
computers and display monitors.
LCDs are of the following two types. One is a simple matrix type
LCD which uses a liquid crystal panel having a liquid crystal layer
sandwiched between a pair of substrates each having a plurality of
electrodes parallel with each other on its inner surface with the
electrodes on one of the pair of the substrates intersecting the
electrodes on the other of the pair. The other is an active matrix
type LCD which uses a liquid crystal panel having a switching
element for selecting each of a plurality of picture elements on
one of a pair of substrates sandwiching a liquid crystal layer
therebetween.
The active matrix type LCD is further classified into two types:
one is a so-called vertical electric field type LCD (commonly
called a TN active matrix type LCD) using a liquid crystal panel in
which electrodes for selecting picture elements are formed on each
of a pair of upper and lower substrates; and the other is a
so-called horizontal electric field type LCD (commonly called an
in-plane switching (IPS) type LCD) using a liquid crystal panel in
which electrodes for selecting picture elements are formed on only
one of a pair of upper and lower substrates.
The liquid crystal panel of the former TN active matrix type LCD is
configured such that liquid crystal molecules are aligned to twist
by 90.degree. between a pair of substrates and a pair of polarizers
are attached on the outer surfaces of the upper and lower
substrates of the liquid crystal panel such that their absorption
axes are in a cross-Nicol arrangement and the absorption axis of
the entrance-side polarizer is parallel or perpendicular to a
direction of rubbing a liquid crystal molecule alignment film
adjacent to the entrance-side polarizer.
In such a TN active matrix type LCD, when no voltage is applied to
the liquid crystal layer, incident light is linearly polarized
through the entrance-side polarizer. The linearly polarized light
propagates along the twisted liquid crystal molecules of the liquid
crystal layer, and if the transmission axis of the exit-side
polarizer conforms to the azimuthal angle of the linearly polarized
light, the linearly polarized light entirely goes out of the
exit-side polarizer to form a white image (so-called normally open
mode).
When a voltage is applied to the liquid crystal layer, directors of
unit vectors each indicating the mean alignment direction of the
molecular axis of each of liquid crystal molecules of the liquid
crystal layer are made perpendicular to the substrate plane, and
they conform to the absorption axis of the exit-side polarizer
because the azimuthal angle of the entrance-side linearly polarized
light is not changed, thereby leading to a black image (see "Basis
and Application of Liquid Crystal" published by Kougyo Chousa Kai
in 1991).
On the other hand, for the IPS type LCD in which electrodes for
selecting picture elements and electrode lines are formed on only
one of a pair of substrates and the liquid crystal layer is
switched in a plane parallel to the substrate by applying a voltage
between two adjacent electrodes (a picture element electrode and a
counter electrode) on the substrate, the polarizers are disposed so
that a black image is formed when no voltage is applied to the
liquid crystal layer (so-called normally close mode).
In the IPS type LCD, molecules of the liquid crystal layer are
parallel to the substrate and in a homogeneous alignment. In the
case where no voltage is applied to the liquid crystal layer,
directors of the liquid crystal layer in a plane parallel to the
substrate are parallel to the arrangement direction of the
electrodes or inclined therefrom at a small angle. On the other
hand, in the case where a voltage is applied to the liquid crystal
layer, the direction of the directors of the liquid crystal layer
is shifted in the direction perpendicular to the arrangement
direction of the electrodes along with the applied voltage to the
liquid crystal layer, and when the direction of the directors of
the liquid crystal layer is inclined by 45.degree. toward the
electrode lines with respect to the direction of the directors of
the liquid crystal molecules in the case where no voltage is
applied to the liquid crystal layer, the liquid crystal layer turns
the azimuthal angle of the plane of vibration of the polarized
light by 90.degree. like a half-wave plate. At this time, since the
transmission axis of the exit-side polarizer conforms to the
azimuthal angle of the plane of vibration of the polarized light,
the polarized light going out of the exit-side polarizer forms a
white image.
The IPS type LCD is advantageous in that the hue and contrast are
less changed even if the viewing angle is changed, to increase an
acceptable range of viewing angles (see Japanese Patent Laid-open
No. Hei 5-505247).
A color-filter method is mainly used to manufacture the
above-described LCDs of a full color type. In this method, a
picture element equivalent to one dot of color display is divided
into three parts, and three color filters equivalent to three
primary colors, that is, red (R), green (G) and blue (B) are
assigned to the above three divided parts of the picture
element.
The present invention can be applied to the above-described various
kinds of LCDs, and hereinafter, the present invention will be
briefly described by example of the TN active matrix type LCD.
As described above, in a liquid crystal display element (also
called liquid crystal panel) constituting part of the TN active
matrix type LCD (hereinafter, referred to simply as "active matrix
LCD"), a plurality of gate lines extending in an X direction and
arranged in a y direction, and drain lines insulated from the gate
lines, extending in the y direction and arranged in the x direction
are formed on the surface, on the liquid crystal layer side, of one
of two transparent insulating substrates (made from glass or the
like) oppositely disposed with a liquid crystal layer put
therebetween.
Each of areas enclosed by these gate lines and drain lines
constitutes a picture element area in which a thin film transistor
(TFT) as a switching element and a transparent picture element
electrode are formed.
When a scanning signal is supplied to the gate line, the thin film
transistor is turned on, and in such a state, a video signal is
supplied to the picture element electrode from the drain line via
the thin film transistor thus turned on.
Not only the drain lines but also the gate lines extend to the
periphery of the substrate to form external terminals, and a video
driver circuit and a gate scanning driver circuit, that is, a
plurality of driver ICs (semiconductor integrated circuits)
constituting the video driver circuit and gate scanning driver
circuit are mounted at the periphery of the substrate in such a
manner as to be connected to the associated external terminals.
That is to say, a plurality of tape carrier packages on each of
which the driver ICs are mounted are mounted at the periphery of
the substrate.
In such a substrate, however, since the TCPs on each of which the
driver ICs are mounted are mounted at the periphery of the
substrate, the area of a region (usually called a frame border)
between the display area composed of intersections between the gate
lines and drain lines of the substrate and the outer edges of the
substrate becomes large, so that it becomes difficult to satisfy a
requirement to reduce the outer size of the liquid crystal display
module in which the liquid crystal display element is integrated
with an illuminating light source (backlight) and other optical
components.
To solve such a problem, that is, to satisfy the requirement
against high density mounting of a liquid crystal display element
and miniaturization of the outer shape of a liquid crystal display
module, there has been proposed a so-called flip-chip method or
chip-on-glass (COG) method in which video driver ICs and scanning
driver ICs are directly mounted on a substrate without the use of
the TCP parts.
A liquid crystal display device manufactured using the flip-chip
method has been disclosed by the present applicant in Japanese
Patent Laid-open No. Hei 6-256426.
The liquid crystal display device disclosed in the above document
comprises: a liquid crystal display element (also called a liquid
crystal display panel or a liquid crystal panel) comprising a pair
of substrates made of glass or the like fixed to one another with a
desired spacing therebetween by a sealing material disposed in a
form of a frame in the vicinity of the edges of the substrates,
transparent electrodes for displaying and liquid crystal molecule
alignment films coated on the opposing inner surfaces of the
substrates, liquid crystal material injected into a space enclosed
by the substrates and the sealing material via an opening provided
in the sealing material, and a pair of polarizers attached on the
outer surfaces of the substrates; a backlight, disposed on the rear
surface of the liquid crystal display element, for supplying light
to the liquid crystal display element; a liquid crystal driver
circuit board disposed around the outer edges of the liquid crystal
display element; a molded lower case for housing and holding the
backlight; and a metal shield case (also called an upper case or
upper frame), having a display window, for housing the above
components.
The backlight comprises an approximately rectangular light guide,
formed of a synthetic resin plate, for example, a transparent
acrylic resin plate, for directing the light from the light source
away from the light source and uniformly illuminating the entire
liquid crystal display element from the rear surface thereof with
the light; a line light source (a fluorescent lamp such as a cold
cathode fluorescent lamp) disposed in the vicinity of at least one
end surface (one side surface) of the light guide in such a manner
as to extend in parallel to the end surface of the light guide; a
light reflector, formed into an approximately U-shape in
cross-section and having an inner surface taken as a reflection
surface, for covering the fluorescent lamp substantially over the
overall length thereof; a light-diffusing sheet disposed on the
light guide, having an upper surface taken as a prismatic surface
formed by a large number of long prisms having a triangular cross
section and arranged parallel with each other and having a lower
surface taken as a smoothing surface, for controlling the angles at
which the light from the backlight and which are otherwise varied
in a wide range, within a specified range and diffusing the light
emerged from the light guide; a prismatic sheet for improving the
luminance of the backlight; and a reflecting sheet, disposed under
the light guide, for reflecting the light emerged from the light
guide toward the liquid crystal display element.
In the prior art LCD, a flexible circuit board provided at a
peripheral portion on the rear surface of the liquid crystal
display element is electrically connected to an upper case as a
metal frame by soldering, with a spring metal piece interposed
between the inner surface of the upper case and the circuit
board.
However, with the advance of the reduction of the frame border
area, there occurs a problem that it is difficult to carry out the
soldering using such a metal piece, particularly, for the flexible
circuit board for drain drive.
According to the prior art LCD, to suppress the positional offset
between the liquid crystal display element and light guide and
ensure the resistance to shock, the light guide is elastically
fixed to the liquid crystal display element with a rubber cushion
interposed therebetween. With this configuration, however, there
occur problems that foreign matters may permeate between the liquid
crystal display element and light guide (display area), and that
since the width of the rubber cushion becomes narrower with the
advance of the reduction of the frame boarder area, it is difficult
to assemble the light guide with the liquid crystal display
element.
The upper case and the lower case are clamped by crimping a
plurality of crimping nails formed at the bottom edges of the
sidewalls of the upper case, at the rear surface of the lower
case.
These crimping nails are formed by making long narrow cuts in
parallel with the underside of the lower case, in the bottom
portions of the side walls of the upper case, and the upper and
lower cases are clamped by crimping the nails at the underside of
the lower case.
There has been a problem with this structure in that reliability of
clamping of the upper and lower cases is degraded because of
insufficient friction between the crimping nails and the underside
of the lower case due to a small contact area of the crimping nails
with the underside of the lower case.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-described
problems of the prior art and to provide a liquid crystal display
device capable of easily realizing the reduction of the frame
border area.
For achieving the aforesaid object, a liquid crystal display device
according to an embodiment of the present invention includes a
liquid crystal display element having a liquid crystal layer
sandwiched between a pair of upper and lower substrates, a flexible
circuit board disposed around a periphery of the liquid crystal
display element, an illuminating light source including a line
light source, a light guide and a reflector and disposed behind the
liquid crystal display element, an upper case made of metal, having
a sidewall bent back from a periphery of a front portion thereof
and a window corresponding to a useful display area of the liquid
crystal display element, a lower case made of resin for housing the
illuminating light source, the upper case and the lower case being
clamped by crimping a plurality of nails formed in the sidewall of
the upper case at an outer surface of the lower case after stacking
the liquid crystal display element, the flexible circuit board and
the illuminating light source between the upper case and the lower
case, wherein an electrical connection between the upper case and a
grounding pattern formed on the flexible circuit board is made by
at least one component in chip form having a conductive region and
being attached to a portion of the grounding pattern bent over the
lower substrate, and a metal tape having one end thereof being
interposed between opposing portions of the upper and lower cases
which are pressed against each other and the other end thereof
being positioned to be pressed against the conductive region of the
at least one component in chip form.
With this configuration, it is possible to reduce the cost by use
of an easy-to-get small-sized chip component, and it is easy to
electrically connect the grounding pattern of a flexible circuit
board to the upper frame even if the width of the flexible circuit
board becomes narrower along with the reduction of the frame border
area.
For achieving the aforesaid object, a liquid crystal display device
according to another embodiment of the present invention includes a
liquid crystal display element having a liquid crystal layer
sandwiched between a pair of upper and lower substrates, a flexible
circuit board disposed around a periphery of the liquid crystal
display element, an illuminating light source including a line
light source, a light guide and a reflector and disposed behind the
liquid crystal display element, an upper case made of metal, having
a sidewall bent back from a periphery of a front portion thereof
and a window corresponding to a useful display area of the liquid
crystal display element, a lower case made of resin for housing the
illuminating light source, the upper case and said lower case being
clamped by crimping a plurality of nails formed in the sidewall of
the upper case at an outer surface of the lower case after stacking
the liquid crystal display element, the flexible circuit board and
the illuminating light source between the upper case and the lower
case, wherein the light guide and the liquid crystal display
element are pressed against each other, and a rubber cushion is
disposed between the light guide and peripheral portions of the
lower case at least in the vicinity of portions where the upper
case and the lower case are clamped by crimping the plurality of
nails.
With this configuration, it is possible to prevent permeation of
foreign matters between the liquid crystal display element and
light guide, and to improve the resistance to shock of the liquid
crystal display device.
For achieving the aforesaid object, a liquid crystal display device
according to another embodiment of the present invention includes a
liquid crystal display element having a liquid crystal layer
sandwiched between a pair of upper and lower substrates, a flexible
circuit board disposed around a periphery of the liquid crystal
display element, an illuminating light source including a line
light source, a light guide and a reflector and disposed behind the
liquid crystal display element, an upper case made of metal, having
a sidewall bent back from a periphery of a front portion thereof
and a window corresponding to a useful display area of the liquid
crystal display element, a lower case made of resin for housing the
illuminating light source, the upper case and the lower case being
clamped by crimping a plurality of nails formed in the sidewall of
the upper case at an outer surface of the lower case after stacking
the liquid crystal display element, the flexible circuit board and
the illuminating light source between the upper case and the lower
case, wherein the plurality of nails are formed such that the
plurality of nails are crimped in a plane parallel with an
underside of the lower case and have at least one bend before
crimping in cross section parallel to the plane.
With this configuration, it is possible to enlarge the contact area
between the crimping nails and the lower case, and hence to improve
the reliability of crimp-clamping. In addition, the nail may be
bent into various shapes such as a single-stepped shape,
multi-stepped shape or a curved shape.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, in which like reference numerals
designate similar components throughout the figures, and in
which:
FIG. 1 is a sectional view of an essential portion for illustrating
an embodiment of an electrical connection between a flexible
circuit board and an upper case in a LCD of the present
invention;
FIG. 2 is a view illustrating a relative positional relationship
between a ship component and a metal tape shown in FIG. 1;
FIG. 3 is a schematic view illustrating an embodiment of a
structure for housing a light guide of a backlight in a lower case
in the LCD of the present invention;
FIG. 4 is a schematic view illustrating another embodiment of the
structure for housing the light guide of the backlight in the lower
case in the LCD of the present invention;
FIGS. 5A and 5B are schematic views illustrating a further
embodiment of the structure for housing the light guide of the
backlight in the lower case in the LCD of the present invention,
wherein FIG. 5A is an enlarged view of a crimp-clamping structure
between the upper case and lower case; and FIG. 5B is a sectional
view taken on VB--VB of FIG. 5A;
FIGS. 6A and 6B are views of an essential portion for illustrating
an embodiment of the crimp-clamping structure of the present
invention in a state before crimping, wherein FIG. 6A is a plan
view seen from the rear surface of the lower case, and FIG. 6B is a
side view of FIG. 6A;
FIGS. 7A and 7B are views of an essential portion for illustrating
another embodiment of the crimp-clamping structure of the present
invention in a state after crimping, wherein FIG. 7A is a plan view
seen from the rear surface of the lower case, and FIG. 7B is a side
view of FIG. 7A;
FIGS. 8A and 8B are views of an essential portion for illustrating
a further embodiment of the crimp-clamping structure of the present
invention, wherein FIG. 8A shows the state before clamping by
crimping nails, and FIG. 8B shows the state after clamping by the
crimping nails;
FIGS. 9A and 9B are exploded perspective views of one configuration
example of the LCD of the present invention, showing a liquid
crystal display element in a state before it is covered with the
upper case and lower case;
FIG. 10 is an exploded perspective view showing a state after an
illuminating light source (backlight) and various optical-films to
be stacked under the upper case and liquid crystal display element
shown in FIGS. 9A and 9B are housed in the lower case and before
the lower case is clamped to the-upper case;
FIGS. 11A to 11E are views of the assembled LCD, wherein FIG. 11A
is a front view of the liquid crystal display element; and FIGS.
11B to 11E are a rear side view, a right side view, a front side
view and a left side view, respectively;
FIGS. 12A and 12B are views illustrating an interface circuit board
mounted on the rear surface and side surface of the liquid crystal
display module shown in FIGS. 11A to 11E, respectively;
FIG. 13 is a plan view of an essential portion for illustrating an
arrangement between a flexible circuit board for gate drive and a
flexible circuit board for drain drive;
FIG. 14 is an exploded perspective view illustrating the entire
configuration of another example of the LCD of the present
invention;
FIGS. 15A to 15D are views of the assembled liquid crystal display
module, wherein FIGS. 15A to 15D are a front view, a right side
view, a front side view, and a left side view of the module,
respectively.
FIG. 16 is a rear view of the assembled liquid crystal display
module;
FIG. 17 is a front view of a liquid crystal display element with
driver circuit boards, in which the flexible circuit board for gate
drive and the flexible circuit board for drain drive in the state
before being folded are mounted at the outer peripheral portion of
the liquid crystal display element;
FIG. 18 is a rear view of the liquid crystal display element with
driver circuit boards shown in FIG. 17 on which the interface
circuit board is mounted;
FIG. 19 is a rear view showing a state in which the liquid crystal
display element is housed in the shield case;
FIG. 20A is a rear view showing a state in which the liquid crystal
display element is housed in the shield case, and FIG. 20B is a
side view of FIG. 20A;
FIGS. 21A and 21B are a front view and a front side view of the
backlight shown in FIGS. 20A and 20B from which a prismatic sheet
and a light-diffusing sheet are removed, respectively;
FIGS. 22A and 22B are a front view and a front side view, similar
to FIGS. 21A and 23B, showing another configuration example of the
backlight, respectively;
FIGS. 23A to 23E are a front view, a rear side view, a right side
view, a front side view and a left side view of the lower case,
respectively;
FIG. 24 is an enlarged view illustrating each corner of the mold
case shown in FIG. 23A;
FIGS. 25A to 25C are views illustrating a housing portion for
housing the light-guide in the mold case, wherein FIG. 25A is a
plan view of an essential portion;
FIG. 25B shows the conventional structure for each corner shown in
FIG. 25A; and FIG. 25C shows the inventive structure for each
corner;
FIGS. 26A and 26B are a side view and a top view illustrating a
state in which a reflector is disposed in the line light
source;
FIGS. 27A and 27B are views illustrating a multilayer flexible
circuit board for drain drive, wherein FIG. 27A is a rear view
(bottom view) and FIG. 27B is a front view (top view);
FIGS. 28A and 28B are views illustrating an essential portion of a
multilayer flexible circuit board FPC2, wherein FIG. 28A is an
enlarged view of a J portion shown in FIG. 27A, and FIG. 28B is a
side view showing the mounting of the multilayer flexible circuit
board and the folded state thereof;
FIGS. 29A and 29B are views illustrating the multilayer flexible
circuit board for gate drive, wherein FIG. 29A is a rear view
(bottom view) and FIG. 29B is a front view (top view):
FIG. 30 is a wiring diagram showing a connection relationship
between signal lines in the multilayer flexible circuit board and
input signals into the driver ICs on the lower substrate;
FIG. 31 is a view illustrating a state in which the driver ICs are
mounted on the lower substrate of the liquid crystal display
element;
FIG. 32 is a plan view of the peripheral of a portion, on which the
drain driver ICs are mounted, of the lower substrate of the liquid
crystal display element and the vicinity of the cutting line of the
substrate;
FIGS. 33A to 33C are views of the multilayer flexible circuit
board, wherein FIGS. 33A and 33B are sectional views taken on lines
33A--33A and 33B--33B of FIG. 27A, respectively, and FIG. 33C is a
sectional view taken on line 33C--33C of FIG. 27B;
FIG. 34 is a perspective view illustrating the method of mounting
the multilayer flexible circuit board FPC2 by folding and a
connection between the multilayer flexible circuit boards FPCL and
FPC2;
FIGS. 35A and 35B are views illustrating a conductive pattern of a
multilayer wiring portion, wherein FIG. 35A is a plan view showing
the configuration of the surface conductive layer pattern of the
multilayer wiring segment FML portion which is partially shown in
FIG. 27B, and FIG. 35B is a partial enlarged view of the interface
circuit substrate PCB shown in FIG. 27D;
FIG. 36 is a sectional view taken on line 36--36 of the liquid
crystal display element shown in FIG. 31;
FIGS. 37A to 37D are views illustrating the interface circuit board
having a controller section and a power source, wherein FIG. 37A is
a rear view (bottom view); FIG. 37B and 37C are a partial front
side view and a partial lateral side view of a hybrid integrated
circuit HI mounted thereon, respectively; and FIG. 37D is a front
view (top view).
FIG. 38 is a sectional view taken on line 38--38 of the LCD shown
in FIG. 11A;
FIG. 39 is a sectional view taken on line 39--39 of the LCD shown
in FIG. 11A;
FIG. 40 is a sectional view taken on line 40--40 of the LCD shown
in FIG. 11A;
FIG. 41 is a sectional view taken on line 41--41 of the LCD shown
in FIG. 11A;
FIG. 42 is a block diagram illustrating the liquid crystal display
element and the circuit configuration of driver circuits disposed
at the peripheral portion of the liquid crystal display
element;
FIG. 43 is a block diagram showing an equivalent circuit of the
liquid crystal display module;
FIG. 44 is a diagram illustrating the flow of display data and
clock signals to gate drivers and drain drivers;
FIG. 45 is a diagram showing the level and waveform of each of a
common-electrode voltage, a drain voltage, and a gate voltage;
FIG. 46 is a block diagram showing the schematic configuration of
each driver of the liquid crystal display element and the flow of
signals;
FIGS. 47A and 47C are timing charts showing display data inputted
from a host computer into a display control device, and FIGS. 47B
and 47D are timing charts showing signals outputted from the
display control device into the drain drivers and gate drivers;
FIG. 48 is a perspective view of a notebook type personal computer
or word processor on which the liquid crystal display module is
mounted; and
FIG. 49 is a perspective view of another notebook type personal
computer or word processor on which the liquid crystal display
module is mounted.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described
with reference to the drawings.
FIG. 1 is a sectional view of an essential portion of a LCD of the
present invention, illustrating an embodiment of an electrical
connection between a flexible circuit board and an upper case of
the LCD, and FIG. 2 is a view illustrating a relative positional
relationship between a chip component and a metal tape in FIG. 1.
In FIG. 1, reference character MCA designates a lower case (resin
mold or mold case) for housing an illuminating light source (a
backlight) comprising a line light source or a combination of a
line light source and a light guide; SHD is an upper case (shield
case) made of metal; SUB1 is a lower substrate; SUB2 is an upper
substrate; POL1 is a lower polarizer; POL2 is an upper polarizer;
and PNL is a liquid crystal display element.
Reference character IC designates a driver IC directly mounted on
the peripheral portion of the lower substrate SUB1; FPC2 is a
flexible circuit board for drain drive; GNDPT is a grounding
pattern of the flexible circuit board; CHX is a chip component; GC
is a rubber cushion material; and MTP is a metal tape (copper
foil).
In this embodiment, the chip component CHX is configured as a chip
capacitor. The chip component CHX has at its both ends metallized
conductive portions MLZ, and is mounted on the underside of the
flexible circuit board FPC2 provided on the rear surface of the
peripheral portion of the lower substrate SUB1 by soldering or the
like. As shown in FIG. 1, the underside of the chip component CHX
is made in contact with one end of the metal tape MTP placed on the
mold case MCA, and the other end of the metal tape MTP is bent
around the edge of the mold case MCA onto the underside of the mold
case MCA and is sandwiched between the upper frame SHD and the mold
case MCA after they are clamped together by crimping portions of
the upper case SHD at the underside of the mold case MCA.
Clamping two parts together by crimping projections (nails, ears or
tongues, for example) formed in one of the two parts at the surface
of the other may be hereinafter referred to as crimp-clamping.
With this embodiment, it is not required to take into account the
width of the flexible circuit board FPC2 for electric connection
between the flexible circuit board FPC2 and upper frame SHD.
Further, a connection between the chip component CHX and metal tape
MTP can be elastically clamped by forming a recess in the mold case
MCA and disposing the rubber cushion GC in the recess, thereby
improving the reliability in connection.
FIG. 3 is a schematic exploded perspective view illustrating an
embodiment of a structure, of the LCD of the present invention, for
housing the light guide constituting part of the backlight in the
lower case. The lower case (or mold case) MCA is substantially a
frame body having a window MO for housing a light guide GLB while
supporting the peripheral edge of the light guide GLB. To be more
specific, the frame-like rubber cushion GC is disposed along the
frame-like inner periphery of the mold case MCA and the light guide
GLB is mounted on the rubber cushion GC. While not shown, a liquid
crystal display element is made in intimate contact with the upper
surface of the light guide with optical sheets such as a
light-diffusing sheet and a prismatic sheet interposed
therebetween. In such a state, as shown in FIGS. 6A and 6B, FIG.
10, FIGS. 11A to 11E, and FIGS. 38 and 41, the upper case SHD is
placed on the liquid crystal display element, and the liquid
crystal display element and upper case SHD are clamped together by
crimping nails formed from the sidewalls of the upper case SHD at
the rear surface of the mold case MCA.
With this configuration, there can be realized a LCD capable of
preventing permeation of foreign particles between the liquid
crystal display element and light guide GLB, and ensuring an
installation space of the rubber cushion so as to enhance the
resistance to shock even in the case of reduction of the frame
boarder area and/or thinning of the LCD.
FIG. 4 is a schematic exploded perspective view illustrating
another embodiment of the structure, of the LCD of the present
invention, for housing the liquid guide constituting part of the
backlight in the lower case. In this embodiment, the rubber cushion
shown in FIG. 3 is divided into four parts corresponding to four
sides of the mold case MCA. The effect of this embodiment is the
same as that in the embodiment shown in FIG. 3. Incidentally,
rubber cushions GC may be interposed between the upper case SHD and
the mold case MCA only in portions where they are
crimp-clamped.
FIGS. 5A and 5B are schematic views illustrating a further
embodiment of the structure, of the LCD of the present invention,
for housing the liquid guide constituting part of the backlight in
the lower case, wherein FIG. 5A is an enlarged view of
crimp-clamped portions between the upper case SHD and the mold case
MCA as the lower case, and FIG. 5B is a sectional view taken on
line VB--VB of FIG. 5A. In this embodiment, in place of the
configuration using the rubber cushion GC shown in FIGS. 3 and 4,
there is adopted a configuration that the thickness of a bottom
side inner peripheral portion MCA-C, for receiving the light guide
GLB, of the mold case MCA is thinned to enhance the elasticity
thereof against the light guide GLB. In addition, the thinned wall
portion MCA-C may be formed at only the crimp-clamped portions of
the mold case MCA with the upper case SHD.
FIGS. 6A and 6B and FIGS. 7A and 7B are views of an essential
portion for illustrating an embodiment of a crimp-clamping
structure according to the present invention, wherein FIGS. 6A and
7A are plan views seen from the rear surface of the lower case, and
FIGS. 6B and 7B are side views of FIGS. 6A and 7A.
The crimp-clamping between the upper case SHD and lower case MCA is
performed such that as shown in FIGS. 6A and 6B, each nail NL
formed on the side surface of the upper case SHD is previously
outwardly bent (shown by an arrow B), and as shown in FIGS. 7A and
7B, such a nail NL is forcibly bent along a bending line BL to be
fixed in a fixing recess NR of the lower case MCA. It may be
desirable that the tip area of the nail NR be previously bent at
such an angle as to be in contact with an inner wall NRW of the
fixing recess NR in parallel upon crimp-clamping.
With this configuration, the contact area of the nails NL and each
of the bottom surface and inner wall of the fixing recess NR
becomes larger, to sufficiently firm crimp-clamping even in the
case of the reduction of the frame border area.
FIGS. 8A and 8B are views of an essential portion for illustrating
another embodiment of the crimp-clamping structure according to the
present invention. The nail NL may be previously curved as shown in
FIG. 8A or may be formed into a wavy shape. In other words, the
nail NL may be formed into any shape insofar as the contact area
between the nails NL and each of the bottom surface and inner wall
of the fixing recess NR becomes large upon crimp-clamping as shown
in FIG. 8A.
In the above embodiments, the chip capacitor is used as the chip
component CHX; however, the present invention is not limited
thereto. For example, a chip resistor, a metallized layer provided
on a ceramic substrate or a metal sheet may be used. Each of the
width, length, and thickness of the chip component is preferably in
a range of 2 mm or less.
Next, examples of LCDs to which the above-described embodiments are
applied will be described in detail. In the following figures,
parts having the same function are designated by the same reference
characters and the repeated explanation thereof is omitted.
FIGS. 9A and 9B and FIG. 10 are exploded perspective views
illustrating the whole of one configuration example of a LCD of the
present invention, wherein FIGS. 9A and 9B are exploded perspective
views showing a state before a liquid crystal display element is
covered with an upper case constituting a housing of the LCD; and
FIG. 10 is an exploded perspective view showing a state after an
illuminating light source (backlight) and various optical films to
be stacked under the upper case and liquid crystal display element
shown in FIGS. 9A and 9B are housed in a lower case and before the
lower case is fixed with the upper case shown in FIG. 9A.
In FIGS. 9A and 9B and FIG. 10, reference character SHD designates
an upper case (shield case); PNL is a liquid crystal element; SPC
(SPC1, SPC2) is an insulating spacer; SCP-P is projections of the
spacer SPC (to be fitted in holes opened in the upper case SHD);
BAT is an adhesive double coated tape; FPC1 and FPC2 are multilayer
flexible circuit boards (FPCL is the circuit board for gate drive
and FPC2 is the circuit board for drain drive); PCB is an interface
circuit board; SPS is a light-diffusing sheet; PRS is a prismatic
sheet; GLB is a light guide; RFS is a reflecting sheet; GC is a
rubber cushion; MCA is a lower case (mold frame); LP is a cold
cathode fluorescent lamp (CFL); LS is a light source reflector; and
LPCH is a cable holder for the cold cathode fluorescent lamp.
The shield case SHD shown in FIG. 9A is made by press-forming and
bending one metal sheet. In FIG. 9A, reference character WD
designates an opening from which the liquid crystal display element
PNL is exposed. The liquid crystal display element PNL is
configured such that a liquid crystal layer is held between two
substrates, and a plurality of gate lines and a plurality of drain
lines intersecting the gate lines are arranged on the lower
substrate, wherein thin film transistors are arranged at
intersections between the gate lines and drain lines and one
picture element electrode driven by one thin film transistor
constitutes one picture element.
The gate driver ICs are mounted on a first side of the lower
substrate adjacent to the interface circuit board PCB of the liquid
crystal display element PNL, and drive signals are supplied to the
gate driver ICs from the flexible circuit board FCP1. The drain
driver ICs are mounted on a second side of the lower substrate
intersecting the first side of the lower substrate, and driver
signals are supplied to the drain driver ICs from the flexible
circuit board FCP2.
The liquid crystal display element on which the above-described
driver ICs, flexible circuit boards FCPL and FCP2, and interface
circuit board PCB are mounted is hereinafter referred to as "liquid
crystal display element with the peripheral circuits, ASB".
Referring to FIG. 10, the light guide GLB is attached inside the
lower case MCA via the rubber cushion GC. The reflecting sheet RFS
is stacked on the rear surface of the light guide GLB. Two pieces
of the prismatic sheets PRS (PRS1 and PRS2) and the light-diffusing
sheet SPS are stacked on the upper surface of the light guide GLB,
and the liquid crystal display element ASB with the peripheral
circuits shown in FIGS. 9A and 9B is mounted thereon and is covered
with the upper case SHD. Then, fixing nails NL formed along the
peripheral edge of the upper case SHD are fitted in fixing recessed
formed in the lower case MCA, to clamp the upper case SHD and lower
case MCA to each other, thereby assembling a LCD (also called
liquid crystal display module).
Next, the configuration examples of the LCD according to the
present invention will be described in more detail with reference
to FIGS. 11A and the later figures.
While there are slight differences between configurations shown in
the accompanying drawings of this specification, it should be
understood that such differences mean that the present invention
can be applied to a plurality of types of LCDs.
FIGS. 11A to 11E are views of the LCD (liquid crystal display
module) showing a state after completion of assembling the liquid
crystal display module, wherein FIG. 11A is a front view of the
liquid crystal display module seen from the front side of the
liquid crystal display element PNL, that is, from the liquid
crystal display element PNL side; and FIGS. 11B to 11E are side
views of the liquid crystal display module. FIG. 12A is a view
illustrating the rear surface of the liquid crystal display module
shown in FIGS. 11A to 11E and the interface circuit board mounted
on the side surface thereof.
The liquid crystal display module MDL has two kinds of
housing/holding members, that is, the lower case (mold frame) MCA
and the upper case (shield frame SHD). In FIG. 11A, reference
character HLD designates four pieces of mounting holes provided for
mounting the module MDL, as a display unit, on an information
processing apparatus such as a personal computer or word processor.
The mounting holes HLD are formed in the shield frame SHD at
positions corresponding to those of mounting holes MH formed in the
mold case MCA (enlargedly shown in FIG. 24). The module MDL is
fixedly mounted on an information processing apparatus by making
screws or the like pass through both the mounting holes. In this
module MDL, an inverter power source for the backlight is disposed
at an MI section (see FIG. 20A), and a power is supplied to the
backlight BL therefrom via a connector LCT and a lamp cable
LPC.
Signals from a host computer and a necessary power are supplied to
a controller section and a power source of the liquid crystal
display module MDL via an interface connector CT1 of the interface
circuit board positioned on the rear surface of the module,
respectively.
FIG. 12B is a view illustrating the configuration example of the
interface circuit board PCB. On the interface circuit board PCB are
mounted the connector CT1 for receiving signals from the host
computer and a necessary power; a low-voltage difference signal
receiving circuit chip LVDS for converting serial low-voltage
difference signals having been received from the host computer into
original parallel signals; a control circuit chip TCON; a
digital/digital converter circuit chip DD for creating various DC
voltages; and connectors CT3 and CT2 for connecting the flexible
circuit board FPC1 for gate drive and the flexible circuit board
FPC2 for drain drive to each other (which will be described
later).
FIG. 13 is a detailed plan view illustrating an arrangement between
the flexible circuit board FPC1 for gate drive and the flexible
circuit board FPC2 for drain drive. The gate driver ICs are mounted
on the upper surface of the liquid crystal element PNL on the
interface circuit board side, and the flexible circuit board FPC1
for gate drive, which is connected to the gate driver ICs, is
disposed. The drain driver ICs are mounted on the bottom side of
the liquid crystal display element PNL, and the flexible circuit
board FPC2 for drain drive, which is connected to the drain driver
ICs, is disposed.
A projection JN4 is formed at an end portion, on the side of the
flexible circuit board FPC1 for gate drive, of the flexible circuit
board FPC2, and a connect or (flat connector) CT4 to be connected
to a connector CT2 of the interface circuit board PCB is provided
at the leading end of the projection JN4. The flexible circuit
board FPC2 is folded on the rear surface of the liquid crystal
element PNL and the connector CT4 is connected to the connector CT2
of the interface circuit board.
FIG. 14 is an exploded perspective view illustrating the entire
configuration of another example of the LCD according to the
present invention. Reference numeral SHD designates an upper case
(shield case); WD is a display window; SPC1 to SPC4 are insulating
spacers; FPC1 and FPC2 are folded multilayer flexible circuit
boards (FPC1 is the circuit board for gate drive and FPC 2 is the
circuit board for drain drive); PCB is an interface circuit board;
ASB is an assembled liquid crystal display element with the driver
circuit boards; PNL is a liquid crystal display element having
driver ICs mounted on one of a pair of transparent insulating
substrates overlapped and fixed with a spacing therebetween; SPS is
a light-diffusing element; GLB is a light guide; RFS is a
reflecting sheet; MCA is a lower case (mold case) formed by
integral molding; LP is a line light source (cold cathode
fluorescent lamp); LPC1 and LPC2 are lamp cables; LCT is a
connector for an inverter power source; and GB is a rubber bush for
indicating the cold cathode fluorescent lamp. These components are
stacked under the vertical arrangement relationship shown in FIG.
14, following by clamping the upper case SHD and lower case MCA to
each other, to thereby assemble a LCD (liquid crystal display
module). The details of the other configuration will be described
later.
FIGS. 15A to 15D are views of the liquid crystal display module
showing a state after completion of assembling the liquid crystal
display module. FIG. 15A is a front view seen from the front side
of the liquid crystal element PNL, that is, from the upper side (or
display side) of the module, and FIGS. 15B to 15D are a right side
view, front side view, and left side view of the module,
respectively.
FIG. 16 is a rear view of the liquid crystal display module, seen
from the rear surface side (that is, lower side) of the liquid
crystal display element PNL, showing a state after completion of
assembling the liquid crystal display module.
The liquid crystal display module MDL has two kinds of
housing/holding members, that is, the mold frame MCA and the shield
frame SHD. Reference character HLD designates four pieces of
mounting holes provided for mounting the module MDL, as a display
unit, on an information processing apparatus such as a personal
computer or word processor. As shown in FIG. 19, the mounting holes
HLD are formed in the shield frame SHD at positions corresponding
to those of mounting holes MH formed in the mold case MCA (see
later figures, FIGS. 23A to 23E and FIG. 24). The module MDL is
fixedly mounted on an information processing apparatus by making
screws or the like pass through both the mounting holes. In this
module MDL, an inverter power source for the backlight is disposed
at an MI section (see FIG. 23A), and a power is supplied to the
backlight BL therefrom via the connector LCT and lamp cable
LPC.
Signals from a host computer and necessary power are supplied to a
controller section and a power source of the liquid crystal display
module MDL via the interface connector CT1 of the interface circuit
board positioned on the rear surface of the module,
respectively.
FIG. 42 is a block diagram showing a TFT liquid crystal display
element of the liquid crystal display module shown in FIG. 19 and
circuits disposed in the peripheral portion of the TFT liquid
crystal display element. In this configuration example, while not
shown, the drain drivers IC.sub.1 to IC.sub.M are mounted, together
with extension lines DTM for drain drive and extension lines GTM
for gate drive formed on one of the substrates of the liquid
crystal display element, by the chip-on-glass method using an
anisotropic conductive film or ultraviolet hardening resin.
In this configuration example, M-pieces of the drain drivers IC and
N-pieces of the gate drivers IC are mounted by the chip-on-glass
method in accordance with useful dots of 800.times.3.times.600
pieces specified under the XGA Specification. In addition, a drain
driver section 103 is disposed on the bottom side of the liquid
crystal display element; a gate driver section 104 is disposed on
the left side portion thereof; and a controller section 101 and a
power source 102 are disposed on the same left side portion
thereof. The controller section 101 and power source 102 are
connected to the gate driver section 104 via an electrically
connecting means JN1 and connected to the drain driver section 103
via an electrically connecting means JN2. The controller section
101 and power source 102 are disposed on the rear surface of the
gate driver section 104.
Next, the configuration of each component will be described in
detail.
Shield Case Made of Metal
FIGS. 15A to 15D are a top view, a right side view, a front side
view, and a left side view of a shield case SHD, respectively. A
perspective view, seen from the upper right side, of the shield
case SHD is shown in FIG. 14.
The shield case (metal frame) SHD is manufactured by press-forming
and bending one metal sheet. Reference character WD designates an
opening from which the liquid crystal display element PNL is
exposed, which opening is hereinafter referred to as "display
window".
Reference character NL designates nails for fixing the shield case
SHD and mold case MCA to each other. For example, 12 pieces of the
nails NL are integrally provided on the shield case SHD. Reference
character HK designates hooks for fixing the shield case SHD and
mold case MCA to each other. For example, 6 pieces of the hooks HK
are integrally provided on the shield case SHD. As described with
reference to FIGS. 6A and 6B and FIGS. 7A and 7B, the liquid
crystal display element ABS with the driver circuits is housed in
the shield case SHD, which is in the state before the fixing nails
NL are folded, with the spaces SPC put therebetween, and then the
nails NL are inwardly folded to be inserted in square-shaped fixing
recesses NR provided in the mold case MCA (see FIGS. 6A and 6B).
The folded states of the nails NL are shown in FIGS. 7A and 7B.
The fixing hooks HK are fitted with fixing projections HP provided
on the mold case MCA (see the side view of FIG. 12B), respectively.
In this way, the shield case SHD which holds and houses the liquid
crystal display element ABS with the driver circuits is rigidly
fixed to the mold case MCA which holds and houses the light guide
GLB, cold cathode fluorescent lamp LP and the like.
A thin rubber cushion elongated into the rectangular shape is
provided on the four side edges of the bottom surface (rear surface
of the reflecting sheet) of the light guide GLB (see FIGS. 38 to
41).
The LCD can be simply disassembled and repaired only by extending
the folded nails NL and removing the hooks HK, and accordingly, for
example, the cold cathode fluorescent lamp of the backlight BL can
be easily replaced. Also in this configuration example, since one
side of the LCD is mainly fixed with the hooks HK and the opposed
side of the LCD is fixed with the nails NL, the LCD can be
disassembled not by removing all of the nails but by removing part
of the nails. This makes it easy to repair the LCP and replace the
backlight.
In FIG. 15A, reference character CSP designates through-holes. The
shield case SHD is mounted with fixed pins, which are prepared upon
manufacture, inserted in the through-holes CSP, to accurately set
the relative position between the shield case SHD and another part.
Insulating spacers SPC1 to SPC4 are composed of insulators, both
surfaces of which are coated with adhesive. The insulating spacers
SPC1 to SPC4 are used for fixing the shield case SHD and the liquid
crystal display element ABS with the driver circuits to each other
with gaps equivalent to the thickness of the insulating spacers
certainly kept therebetween.
When the module MDL is mounted on an application product such as a
personal computer, the through-holes CSP can be taken as a
reference for positioning of the module MDL.
Insulating Spacer
As shown in FIGS. 9A and 9B and FIGS. 39 and 40, the insulating
spacers SPC (SPC1 to SPC4) are used not only for ensuring
insulating between the shield case SHD and the liquid crystal
display element ABS with the driver circuits but also for ensuring
the positional accuracy of the liquid crystal display element ABS
with the shield case SHD and fixing the liquid crystal display
element ABS and the shield case SHD to each other with the adhesive
double coated tape BAT.
Multilayer Flexible Circuit Board FPC1, FPC2
FIG. 17 is a front view of a liquid crystal display element with
driver circuit boards, in which the flexible circuit board FPC1 for
gate drive and the flexible circuit board FPC2 for drain drive in
the state before being folded are mounted on the outer peripheral
portion of the liquid crystal display element PNL.
FIG. 16 is a rear view of the liquid crystal display element with
the driver circuit boards shown in FIG. 17, on which the interface
circuit board PCB is mounted.
FIGS. 20A and 20B are a rear view and a side view, respectively,
showing a state in which the flexible circuit boards FPC1 and FPC2
and the interface circuit board PCB are mounted in the shield case
SHD reversely located, and the flexible circuit board FPC2 is
folded and the liquid crystal display element PNL is housed in the
shield case SHD.
In FIG. 17, IC chips on the left side are driver IC chips on the
vertical scanning circuit side, and IC chips on the bottom side are
driver IC chips on the video signal driver circuit side, which are
mounted on the substrate by the chip-on-glass method using an
anisotropic conductive film (see ACF2 in FIG. 36), ultraviolet
hardening agent or the like.
Conventionally, there has been adopted a technique of connecting a
tape carrier package (TCP), on which driver ICs have been mounted
by the tape-automated-bonding method (TAB), to the liquid crystal
display element PNL using an anisotropic conductive film. On the
contrary, according to the chip-on-glass method, since driver ICs
are directly mounted, it is possible to eliminate the above TAB
step and hence to shorten the number of the manufacturing steps,
and since the necessity of the tape carrier is eliminated, it is
possible to reduce the cost. Further, the chip-on-glass method is
suitable for mounting a high-definition/high density liquid crystal
element.
Here, the drain driver ICs are arranged in a row along one long
side of the liquid crystal display element PNL, and the drain lines
are extracted to the one long side. The gate lines are also
extracted to one short side; however, for a higher-definition LCD,
the gate lines can be extracted to opposed two short-sides.
In the method in which the drain lines DTM or gate lines GTM are
alternately extracted, it becomes easy to connect the drain lines
DTM or gate lines GTM to output side bumps BUMP of the driver ICs;
however, it is required to dispose peripheral circuit boards at
outer peripheral portions along opposed two long sides of the
liquid crystal display element PNL. This causes a problem that the
outer size of the LCD becomes larger than that of the LCP in which
the drain lines or gate lines are extracted only to one side. In
particular, for an information processing apparatus required to
display color images, as the number of colors to be displayed is
increased, the number of data lines for display data is increased
and thereby the outermost size of the information processing
apparatus becomes larger. In this regard, according to this
configuration example of the LCD, the drain lines are extracted
only to one side using a multilayer flexible circuit board.
FIGS. 27A and 27B are views illustrating the multilayer flexible
circuit board FPC 2 for drain drive, wherein FIG. 27A is a rear
view (bottom view), and FIG. 27B is a front view (top view). FIGS.
29A and 29B are views illustrating the multilayer flexible circuit
board FPC1 for gate drive, wherein FIG. 29A is a rear view (bottom
view), and FIG. 29B is a front view (top view).
FIGS. 33A to 33C are views illustrating the structure of the
multilayer flexible circuit board FPC2 shown in FIGS. 27A and 27B,
wherein FIG. 33A is a sectional view taken on line 33A--33A of FIG.
27A; FIG. 33B is a sectional view taken on line 33B--33B of FIG.
27A; and FIG. 33C is a sectional view taken on line 33C--33C of
FIG. 27A. It should be noted that the ratio between the scales in
the thickness direction and the planar direction is different from
the actual one in FIGS. 33A to 33C, that is, the cross-sections of
the multilayer flexible circuit board FPC2 are exaggeratedly shown
in FIGS. 33A to 33C for an easy understanding.
FIG. 30 is a schematic wiring diagram showing a connection
relationship between signal lines in the multilayer flexible
circuit board FPC and input signals into the driver ICs on the
substrate SUB1. The signal lines in the multilayer flexible circuit
board FPC include a first group of the lines parallel to one side
of the substrate SUB1 and a second group of the lines perpendicular
thereto. The first group of the lines are adapted to supply signals
common to the driver ICs, and the second group of the lines are
adapted to individually supply signals necessary for the driver
ICs. Accordingly, a projecting portion FSL is composed of at least
one conductive layer, and a segment FML is composed of at least two
conductive layers in which the first group of the lines are
electrically connected to the second group of the lines via
through-holes. In this configuration example, it is required to
shorten the short-side length of the segment FML in order to
prevent the segment FML from being brought into contact with the
lower polarizer when the segment FML is folded.
To be more specific, as shown in FIGS. 33A to 33C, the segment FML
having three or more of conductive layers, for example, eight
layers L1 to L8 in this configuration is provided in parallel to
one side of the liquid crystal display element PNL and peripheral
circuit lines and electronic parts are mounted on the segment FML.
The use of such a segment FML makes it possible to keep up with the
increased number of data lines by increasing the number of the
layers of the segment FML while leaving the outer size of the
circuit board as it is.
The conductive layer L1 is for part pads and grounding; L2 is for a
gray-scale reference voltage V.sub.ref and a 5 V (or 3.3 V) power
source; L3 is for grounding; L4 is for data signals and clock
signals CL2, CL1; L5 is for extraction wires as the second group of
the lines; L6 is for the gray-scale reference voltage V.sub.ref ;
L7 is for data signals; and L8 is for the 5 (or 3.3 V) power
source.
The conductive layers are electrically connected to each other via
through-holes VIA (see FIG. 35A). Each of the conductive layers L1
to L8 are formed of a copper (Cu) film for wiring, and the portion
of the conductive layer L5 to be connected to input terminal lines
Td (see FIGS. 31 and 32) into the driver ICs of the liquid crystal
display element PNL is made from a Cu film on which nickel (Ni) and
gold (Au) are sequentially plated. Accordingly, the connection
resistance between the output terminal TM and input terminal line
Td can be reduced.
An intermediate layer formed of a polyimide film BFI is interposed
between two adjacent ones of the conductive layers L1 to L8 and is
bonded thereto via adhesive layers BIN. The conductive layer is
covered with the insulating layer except for the output terminals
TM, and particularly, at the multilayer wiring segment FML, each of
the uppermost and lowermost layers is coated with a solder resist
SRS for ensuring insulation. Further, an insulating silk material
SLK is stuck on the uppermost surface.
The multilayer flexible circuit board is advantageous in that the
conductive layer L5 connected to the connection terminal portions
TM necessary for COG mounting can be provided integrally with the
other conductive layers, to thereby reduce the number of parts.
The segment FML, which is composed of three or more of the
conductive layers, becomes a hard portion less in deformation, and
therefore, positioning holes FHL can be provided in the segment
FML. Accordingly, the multilayer flexible circuit board can be
folded at a high accuracy and a high reliability without occurrence
of deformation at the segment FML. While will be described in
detail later, a solid conductive pattern ERH or a mesh conductive
pattern ERH provided with a number of fine holes SH each having a
diameter of, for example, about 200 .mu.m (see FIG. 35A) can be
disposed on the surface layer L1, and conductive patterns for
mounting parts and peripheral lines are wired using the remaining
two or more of the conductive layers.
In addition, the projecting portion FSL is not necessarily composed
of a single conductive layer but may be composed of two conductive
layers. This configuration is useful in the following case. If the
pitch of the input terminal lines Td into the driver ICs becomes
narrower, the pattern of each of the terminal lines Td and
connection terminal portions TM is divided into patterns of a
plurality of staggered rows of lines, followed by electrical
connection of the lines with an anisotropic conductive film or the
like, and when the connection terminal portions TM in the first
conductive layer are extracted, the lines in another row are
connected to the second conductive layer via the through-holes VIA.
Also, the configuration of the two conductive layers of the
projecting portion FSL is useful in the case where part of the
peripheral lines are disposed in the second conductive layer in the
projecting portion FSL.
The configuration of two or less of the conductive layers of the
projecting portion FSL improves thermal conductivity upon
heat-press at the heat seal. This makes it possible to uniformly
apply the pressure upon heat-press, and hence to improve the
reliability of electrical connection between the connection
terminal portions TM and terminal lines Td. Also, the multilayer
flexible circuit board can be accurately folded without giving any
bending stress to the connection terminal portions TM. Further,
since the projecting portion FSL is semi-transparent, the pattern
of the conductive layers can be observed from the upper surface
side of the multilayer flexible circuit board, leading to an
advantage that the pattern inspection for connection state or the
like can be performed from the upper surface side of the circuit
board. In FIGS. 27A and 27B, reference character JT2 designates a
recess for electrical connection between the flexible circuit board
FPC2 for drain drive and the interface circuit board PCB; and CT4
is a flat type connector, provided at the leading end of a
projection JT, for electrical connection between the flexible
circuit board FPC2 and interface circuit board PCB.
FIGS. 28A and 28B are views illustrating an essential portion of
the multilayer flexible circuit board FPC2, wherein FIG. 28A is an
enlarged view of a J portion shown in FIG. 27A, and FIG. 28B is a
side view showing the mounting of the multilayer flexible circuit
board FPC2 and the folded state thereof.
Referring to FIG. 28A, reference character P.sub.x designates a
wavelength of the wave at a wavy end of the polyimide film BFI as
the cover layer; P.sub.y is a wave height of the wave (amplitude of
wave.times.2); P.sub.1 is a straight line connecting the crests of
the waves to each other (called crest line of waves); P.sub.2 is a
straight line connecting troughs of the waves to each other (called
trough line of waves); LY2 is a length of the connection between
the multilayer flexible circuit board FPC2 and substrate SUB1
(called connection length); and LY1 is a length between the
connection, with the substrate SUB1, of the multilayer flexible
circuit board FPC2 and the crest line P1 of the waves.
As shown in FIG. 28B, one end of the flexible circuit board FPC2
for drain drive is connected to the terminals for drain lines (Td
in FIGS. 31 and 32) at the end portion of the substrate SUB1 of the
liquid crystal display element PNL via the anisotropic conductive
film ACF; the intermediate portion (wave height: PY) of the circuit
board FPC2 is folded downwardly at the outer edge of the associated
side of the liquid crystal display element PNL; and the other end
(multilayer wiring portion FML) of the circuit board FPC2 is
located on the underside of the substrate 1 and is stuck thereon
with the adhesive double coated tape BAT. It should be noted that
the numbers 1 to 45 assigned to the output terminals TM in FIG. 28A
correspond to the numbers 1 to 45 assigned to the terminals Tg
shown in FIGS. 31 and 32, and the output terminals TM 1 to 45 are
electrically connected to the terminals Tg 1 to 45 via the
anisotropic conductive film ACF1, respectively.
As described above, according to this configuration example, in the
flexible circuit board FPC2 for inputting signals in which one end
is connected to the end portion of the substrate SUB1 of the liquid
crystal display element and the other end is folded on the
underside (or upper surface) of the SUB1, the end portion of the
polyimide film BFI of the projecting portion FSL is formed into a
wavy form (or the shape having the crests and troughs, for example,
a saw-tooth shape) along the folded line, so that it is possible to
disperse the stress concentration at the end portion of the
polyimide film BFI as the folded portion, and hence to form a
desirable curve at the folded portion. This makes it possible to
suppress occurrence of disconnection at the fold portion, and hence
to improve the reliability.
In this configuration example, the multilayer flexible circuit
board FPC1 for gate drive has three conductive layers L1, L2 and
L3. The first layer L1 is for V.sub.dq (10 V), V.sub.sg (5 V), and
V.sub.ss (grounding); the second layer L2 is for extraction wiring,
a clock signal CL3, FLM, and V.sub.dg (10 V); and the third layer
L3 is for V.sub.EG (-10 to -7 V), V.sub.EE (-14 V), V.sub.SG (5 V),
and common-electrode voltage V.sub.com.
Next, alignment marks ALMG (see FIG. 29A) and ALMD (see FIG. 28A)
on the multilayer flexible circuit board will be described.
In each of the multilayer flexible circuit boards FPC1 and FPC2
shown in FIGS. 27A and 27B to FIGS. 29A and 29B, the length of each
output terminal TM is usually set at about 2 mm for ensuring the
reliability of connection. However, since the long side of each of
the flexible circuit boards FPC1 and FPC2 is longer, there occurs a
positional offset between the input terminal line Td and output
terminal TM due to a slight offset in rotational position of the
major axis, tending to cause a connection failure. The alignment
between the liquid crystal display element PNL and each of the
flexible circuit boards FPC1 and FPC2 is performed by inserting
fixing pins in holes FHL opened at both ends of the circuit board,
and aligning several pieces of the input terminal lines Td with the
associated output terminals TM.
According to this configuration example, to further improve the
alignment accuracy, two pieces of the alignment marks ALMG (ALMD)
are provided at each projecting portion FSL of the flexible circuit
board FPC1 (FPC2).
In this configuration example, to improve the reliability of
connection, dummy lines NC are provided at positions adjacent to a
specific number of the input terminals TM and the frame-like
alignment marks ALMG are connected to the dummy lines by
patterning, wherein the alignment is performed by fitting square
solid patterns (on the drain side, see ALC in FIGS. 31 and 32)
formed on the opposed substrate SUB1 in the frame-like alignment
marks ALMG.
A common-electrode voltage is supplied from conductive beads or
paste to a transparent common picture element electrode COM on the
substrate SUB2 side through the pattern of the lines Td on the
substrate SUB1.
The alignment mark ALMG is provided in such a manner as to be
connected by patterning to the terminal electrically connected to
the transparent common picture electrode COM and is aligned with
the square solid pattern ALD formed on the substrate SUB1 (see FIG.
32). Further, in this configuration example, a joint pattern (not
shown) is provided for connection of the lower end of the flexible
circuit board FPC2 for drain drive with the flexible circuit board
FPC1 for gate drive.
Next, the shape of the segment FSL having two or less of the
conductive layers will be described.
The projecting portion FSL composed of a single conductive layer or
two conductive layers is formed into projecting shapes separated
from each other for each drive IC. As a result, it is possible to
prevent occurrence of a phenomenon in which the multilayer flexible
circuit board is thermally expanded in the major axis direction
upon heat-press using a heat tool, to change the pitch P.sub.G
(P.sub.D) of the terminals TM, thereby causing the peeling and
connection failure between the terminals TM and the connection
terminals Td. To be more specific, by forming the projecting
portion FCL into projecting shapes separated from each other for
each drive IC, the deviation in the pitch P.sub.G (P.sub.D) of the
terminals TM can be set at a value equal to or less the thermal
expansion amount of the flexible circuit board corresponding to the
length of the arrangement period of the driver ICs. In this
configuration example, the shape of the projecting portion FSL is
divided into ten pieces along the major axis of the multilayer
circuit board, to reduce the thermal expansion amount of the
circuit board into one-tenth and also relax the stress applied to
the terminals TM, thereby improving the thermal reliability of the
liquid crystal display module MDL.
As described above, since the alignment marks ALMG (ALMD) and the
projecting portion FSL is formed into projecting shapes separated
from each other for each driver IC, even if the number of
connection lines and the number of display data are increased, it
is possible to reduce the size of the peripheral driver circuit
while ensuring the reliability of connection.
Next, the segment FML having three or more of the conductive layers
will be described.
Chip capacitors CHG and CHD are mounted on the segments FML of the
circuit boards FPC1 and FPC2, respectively. To be more specific, in
the multilayer flexible circuit board FPC1 for gate drive, the chip
capacitor CHG is soldered between a ground potential V.sub.ss (0 V)
and a power source V.sub.dg (10 V) or between a power source
V.sub.sg (5 V) and the power source V.sub.dg. On the other hand, in
the flexible circuit board FPC2 for drain drive, the chip capacitor
CHD is soldered between the ground potential V.sub.ss and a power
source V.sub.dd (5 V or 3.3 V) or between the ground potential
V.sub.ss and the power source V.sub.dd. These capacitors CHG and
CHD are mounted for reducing noise superimposed on the power source
line.
In this configuration example, the mounting of the chip capacitor
CHD is designed such that the chip capacitor CHD is soldered only
on the surface conductive layer L1 on one side in order that the
capacitor is positioned on the underside of the substrate SUB1
after folding of the flexible circuit board.
Accordingly, it becomes possible to mount the capacitors for
smoothing the power source noise on the flexible circuit boards
FPC1 and FPC2 respectively while keeping constant the thickness of
the liquid crystal display module MDL.
A method of reducing high frequency noise caused by an information
processing apparatus on which the LCD is mounted will be described
below. Since the shield case SHD side is equivalent to the surface
side of the liquid crystal display module MDL and to the front
surface side of the information processing apparatus, occurrence of
EMI (electromagnetic interference) noise from the surface exerts
adverse effect on the service environment of external equipment. To
cope with such an inconvenience, according to this configuration
example, the surface layer L1 of the conductive segment FML is
covered with the solid or mesh pattern ERH for a DC power source as
needed.
FIGS. 35A and 35B are views illustrating the conductive pattern of
a multilayer wiring portion, wherein FIG. 35A is a plan view
showing the configuration of the surface conductive layer pattern
of the multilayer wiring segment FML portion which is partially
shown in FIG. 27B, and FIG. 35B is a partial enlarged view of the
interface circuit substrate PCB of FIG. 37D.
The mesh MESH is composed of a number of holes each having a
diameter of about 300 .mu.m opened in the surface conductive layer
L1. The mesh pattern ERH covers the surface conductive layer L1
substantially over the entire surface except for the through-holes
VIA and capacitor CHD portion.
In particular, for the active matrix type liquid crystal display
module using thin film transistors, it is difficult to take a
measure against the EMI because the module uses high speed clock.
To prevent the EMI, at one or more portions near the flexible
circuit board FPC2 for drain drive, a grounding wiring (AC
establishing potential) is connected to a common frame being
sufficiently low in impedance (that is, shield case SHD).
By adopting the structure described with reference to FIG. 1 for
such connection, the grounding wiring at a high frequency region is
reinforced, and accordingly, the radiation electric field strength
can be significantly reduced by connecting the grounding wiring at
about five portions for all.
Interface Circuit Board PCB
FIGS. 37A to 37D are views illustrating the interface circuit board
having a controller section and a power source, wherein FIG. 37A is
a rear view (bottom view); FIG. 37B and 37C are a partial front
side view and a partial lateral side view of a hybrid integrated
circuit HI mounted thereon; and FIG. 37D is a front view (top
view).
In this configuration example, the interface circuit board PCB
(hereinafter, also referred to simply as "circuit board PCB") is
configured as a multilayer printed circuit board made from
glass-reinforced epoxy resin. The circuit board PCB can be
configured as a multilayer flexible circuit board; however, since
such a circuit board PCB does not adopt the folding structure, it
is configured as a relatively inexpensive multilayer printed
circuit board.
Electronic parts are all mounted on the bottom surface side of the
circuit board PCB, that is, on the rear surface side as seen from
the information processing apparatus side. One integrated circuit
device TCON as the display control device is disposed on the
circuit board PCB, which device is not housed in a package but is
directly mounted on the circuit board PCB by a ball-grid-array
method.
An interface connector CT1 is mounted on the circuit board PCB at
an approximately central portion thereof, and further a plurality
of resistors and capacitors, the above-described circuit part EMI
for removing high frequency noise, and the like are mounted on the
circuit board PCB.
The hybrid integrated circuit HI is configured such that part of
the circuits are made in hybrid form and a plurality of integrated
circuits and electronic parts mainly for forming supply power
sources are mounted on upper and lower surfaces of a small circuit
board. One piece of such a hybrid integrated circuit HI is mounted
on the interface circuit board PCB.
In this configuration, the electrical connection between the
flexible circuit board FPC1 for gate drive and the interface
circuit board PCB via the electrically connecting means JN1 is
performed using the connector CT3.
FIG. 38 is a sectional view taken on line 38--38 of FIG. 11A; FIG.
39 is a sectional view taken on line 39--39 of FIG. 11A; FIG. 40 is
a sectional view taken on line 40--40 of FIG. 11A; and FIG. 41 is a
sectional view taken on line 41--41 of FIG. 11A.
Referring to FIG. 39, when viewed in the direction perpendicular to
the substrates SUB1 and SUB2 constituting part of the liquid
crystal display element PNL, the interface circuit board PCB is
partially overlapped to the liquid crystal display element PNL and
is disposed on the underside of the bottom surface of the substrate
SUB1. One end of the flexible circuit board FPC1 for gate drive is
directly electrically, mechanically connected to the substrate SUB1
of the liquid crystal display element PNL, and the circuit board
FPC1 is not folded unlike the circuit board FPC2 for drain drive
and is overlapped on the interface circuit board PCB substantially
throughout the width of the circuit board FPC1.
By partially overlapping the interface circuit board PCB to the
substrate SUB1 of the liquid crystal display element PNL and
further overlapping the circuit board FPC1 for gate drive on the
interface circuit board PCB as described above, it is possible to
reduce the width and area of the frame border portion, and hence to
reduce the outer size of the liquid crystal display element and an
information processing apparatus such as a personal computer or
word processor in which the liquid crystal display element is
incorporated as a display section.
The liquid crystal display element PNL is fixed to the shield case
SHD by providing the spacer SPC made from resin or the like between
the lower substrate SUB1 of the liquid crystal display element PNL
and the shield case SHD and interposing the adhesive double coated
tapes BAT between the upper surface of the spacer SPC and the
shield case SHD and between the lower surface of the spacer SPC and
the substrate SUB1.
The shield case SHD has a plurality of holes HOLS opened along the
long sides, into which projections SPC2-P formed on the spacer SPC
are fitted to prevent the offset of the spacer SPC.
Liquid Crystal Display Element ABS With Drive Circuit Board
Referring to FIG. 39, the flexible circuit board FPC2 for drain
drive is folded and bonded on the surface, opposite to the pattern
formation surface, of the substrate SUB1. The polarizers POL1 and
POL2 extend inwardly up to a position separated from the useful
display area AR by only a slight distance (about 1 mm), and the end
portion of the circuit board FPC2 is located at a position
separated from the above position of the polarizers by a distance
of about 1 to 2 mm.
The distance from the end of the substrate SUB1 to the projecting
end of the folded portion of the circuit board FPC2 is as very
small as about 1 mm, which allows the compact mounting.
Accordingly, in this configuration example, the distance from the
useful display area AR to the projecting end of the folded portion
of the circuit board FPC2 becomes about 7.5 mm.
FIG. 34 is a perspective view illustrating the method of mounting
the multilayer flexible circuit board by folding.
The flexible circuit board FPC2 for drain drive is connected to the
flexible circuit board FPC1 for gate drive using as a joiner the
flat connector CT4 provided at the leading end of the projection
JT2 which is composed of a flexible circuit board integrated with
the circuit board FPC2.
The flat connector CT4 is provided on the surface side of the
projection JT2. The projection JT2 is bent in the direction shown
by reference character BENT1 around a line BTL and then bent in the
direction shown by reference character BENT2, and the flat
connector CT4 is connected to the connector CT2 of the interface
circuit board PCB (see FIG. 39). In addition, the circuit board
FPC2 is fixed on the substrate SUB1 with the adhesive double coated
tape interposed between the circuit board FPC2 and the substrate
SUB1.
Rubber Cushion GC
The rubber cushion GC is, as shown in FIG. 10 and FIGS. 38 to 41,
is interposed between the reflecting sheet disposed on the
underside of the light guide GLB and the mold case MCA for fixing
the light guide GLB and liquid crystal display element PNL between
the shield case SHD and mold case MCA by making use of the
elasticity of the rubber cushion GC. While the rubber cushion GC is
disposed along the periphery of the light guide GLB, it may be only
interposed at positions between the nails NL formed on the shield
case SHD and the engagement portions formed on the mold case
MCA.
At least one surface of the rubber cushion GC is coated with an
adhesive, or adhesive double coated tapes may be stuck on both the
surfaces of the rubber cushion GC, and the rubber cushion GC which
is stuck on one of the light guide GLB and mold case MCA fixes the
other.
Backlight BL
As shown in FIG. 38, the backlight BL includes the light guide GLB,
optical sheet members such as the light-diffusing sheet SPC and
prismatic sheet PRS, the reflecting sheet RFS provided on the
underside of the light guide GLB, the line light source (cold
cathode fluorescent lamp) LP provided along one end surface of the
light guide GLB, and the light source reflector LS. These members
are housed in the recess of the mold case MCA.
The light source reflector LS is disposed over the line light
source LP along the major axis of the line light source LP, and is
fixed on the edges of the light guide GLB (on the prismatic sheet
PRS) and on the edges of the mold case MCA with the adhesive double
coated tape BAT.
In the configuration example, the reflecting sheet RFS disposed on
the underside of the light guide GLB extends up to the position
under the line light source LP, so that the extension portion RFS-E
is taken as the lower light source reflector. The lower light
source reflector, however, is not necessarily required, the inner
surface of the mold case MCA may be configured to have the light
reflectance (specular or white color). Since the light emitted from
the line light source LP and reflected from the inner wall side
opposite to the light guide GLB of the line light source LP is
almost blocked by the line light source LP, the reflector is not
required to be provided thereat; however, in the case where a gap
between the line light source LP and the lower surface of the
reflector LS or the mold case MCA becomes large, the inner wall
(including the bottom surface) of the mold case MCA may be
configured to have the light reflectance (specular or white color)
for improving the light usability.
FIGS. 20A and 20B are a front view (on the liquid crystal display
PNL side) and a side view of the backlight BL; FIGS. 21A and 21B
are a front view and a side view of the backlight shown in FIGS.
15A to 15D from which the prismatic sheet PRS and light-diffusing
sheet SRS are removed; and FIGS. 22A and 22B are a front view and a
side view of another configuration example of the backlight.
The lamp cables LPC (LPC1, LPC2) of the cold cathode fluorescent
lamp as the line light source LP are wired on the side surface of
the liquid crystal display element PNL and receive a power from an
inverter power source circuit board (not shown) via the lamp
connector LCT. In addition, reference character GB designates a
rubber bush for holding the lamp cable LPC.
Light-Diffusing Sheet SPS
The light-diffusing sheet SPS is mounted on the light guide GLB,
and is adapted to diffuse light having emerged from the upper
surface of the light guide GLB for uniformly illuminating the
liquid crystal display element PNL.
Prismatic Sheet PRS
In this configuration example, the prismatic sheet PRS is a
combination of two prismatic sheets each having a smooth bottom
surface and a prismatic top surface, and is mounted on the
light-diffusing sheet SPS such that the prismatic grooves of the
stacked two prismatic sheets are made perpendicular to each other.
The prismatic sheet PRS is adapted for collecting the light having
emerged from the light-diffusing sheet SPS toward the liquid
crystal display element PNL, to improve the luminance of the
backlight BL, thereby reducing the power consumption of the
backlight, and realizing the miniaturization and lightweightness of
the liquid crystal display module.
Each of the light-diffusing sheet SPS and prismatic sheet PRS has,
at the end portions of one side, two pieces of fixing small holes
SLV which are to be aligned with each other when both the sheets
are mounted. On the other hand, the mold case MCA has, at the
corresponding end portions of one side, pin-like projections MPN
which are to be inserted in the small holes SLV of both the sheets
SPS and PRS via sleeves SLV for alignment of both the sheets with
the mold case MCA. The sleeve SLV is made from an elastic body such
as silicon rubber, and it has an inside diameter smaller than the
outside diameter of the projection MPN for preventing the falling
of the sleeve SLV from the projection MPN.
As shown in FIG. 24, the light-diffusing sheet SPS and prismatic
sheet PRS can be more accurately aligned with the mold case MCA by
inserting, on the side opposite to the line light source LP, the
small holes provided in both the light-diffusing sheet SPS and
prismatic sheet PRS around the pin-like projections MPN integrally
provided on the end portions of the above side of the mold case
MCA.
Since the projections MPN are located at positions not overlapped
in a plan view to the circuit board PCB under the flexible circuit
board FPC1 for gate drive, the thickness of the liquid crystal
display module is not increased by provision of the projections
MPN.
Mold Case MCA
FIGS. 23A to 23E are views illustrating the mold case MCA, and FIG.
24 is an enlarged view of an A portion, B portion, C portion and D
portion shown in FIG. 23A. The mold case MCA is formed by integral
molding from a synthetic resin using one mold, and is used as the
backlight housing lower case for holding the cold cathode
fluorescent lamp LP, lamp cable LPC, light guide GLB and the
like.
The mold case MCA is rigidly integrated with the metal made shield
case SHD by means of respective fixing members and the action of
the elastic body, to improve the resistance to vibration and
thermal shock of the liquid crystal display module MDL, thereby
enhancing the reliability thereof.
The bottom surface of the mold case MCA has, at the central portion
excluding the peripheral frame-like portion, a large opening MO
having an area being as large as half or more the total area of the
bottom surface. The provision of such a large opening MO prevents
an inconvenience that the bottom surface of the mold case MCA may
be bulged, after assembly of the mold case MCA, by a force applied
to the bottom surface of the mold case MCA from top to bottom in
the vertical direction due to the action of the rubber cushion GC
mounted between the backlight BL and mold case MCA, thereby
suppressing the increase in maximum thickness of the mold case MCA.
This contributes to the thinning and lightweightness of the liquid
crystal display module MDL.
In FIG. 24, reference character MCL designates cutouts (including a
cutout for connection of the connector CT1) provided in the mold
case MCA at positions corresponding to mounting positions of
heat-generation parts (the power source circuit DC--DC converter DD
shown in FIGS. 37A to 37D and the like) of the interface circuit
board PCB.
The provision of the cutouts at the positions corresponding to the
mounting positions of the heat-generation parts on the interface
circuit board PCB without covering them with the mold case MCA is
effective to enhance the heat radiation of the heat-generation
parts on the interface circuit board PCB. Since the integrated
circuit TCON for display control is also regarded as the
heat-generation part, a cutout may be provided in the mold case MCA
at the corresponding position over the integrated circuit TCON.
In FIGS. 23A to 23E and FIG. 24, reference character MH designates
four pieces of mounting holes used for mounting the liquid crystal
display module MDL on an application apparatus such as a personal
computer. The shield case SHD has mounting holes HLD corresponding
to the mounting holes MH formed in the mold case-MCA. The module
MDL is fixedly mounted on an application apparatus by means of
screws or the like passing through these mounting holes MH and
HLD.
In FIGS. 23A to 23E and FIG. 24, reference character MB designates
a holding portion for holding the light guide GLB; PJ is a
positioning portion; and MC1 to MC4 are housing portions for
housing the lamp cables LPC1 and LPC2. Housing of Light-Guide GLB
in Mold Case MCA
FIGS. 25A to 25C are views illustrating the housing portion for
housing the light-guide GLB in the mold case MCA, wherein FIG. 25A
is a plan view of an essential portion; FIG. 25B shows the
conventional structure at each corner; and FIG. 25C shows the
structure of each corner according to this configuration
example.
As shown in FIG. 25A, four corners of the light guide GLB are
beveled into straight-slop portions, and the straight-slope
positioning portions PJ corresponding to the straight-slope
portions of the light guide GLB are formed at the four corners of
the mold case MCA. According to the conventional structure, as
shown in FIG. 25B, since the positioning portion PJ at each corner
has a right-angled step, it does not sufficiently exhibit the
resistance against a force F applied along the side of the
light-guide GLB (in the y direction), whereby the positioning
portion PJ may be broken by vibration and shock applied from the
heavy light guide GLB.
According to this configuration example, as shown in FIG. 25C,
since each corner of the light guide GLB and the positioning
portion PJ at the corresponding corner of the mold case MCA are
sloped, a force applied to the positioning portion PJ is dispersed
into two-directional components fx and fy, to prevent the breakage
of the positioning portion PJ, thereby improving the reliability of
housing.
Arrangement of Cold Cathode Fluorescent Lamp LP and Light Source
Reflector LS
As shown in FIG. 25A, the light source reflector LS is fixed on the
upper side of the line light source (cold cathode fluorescent lamp)
LP using an adhesive double coated tape in such a manner as to
bridge the light guide GLB and mold case MCA together. The
cross-sectional structure of such a portion is shown in FIG.
38.
To be more specific, as shown in FIG. 38, the cold cathode
fluorescent lamp LP as the line light source is disposed in
proximity to one end surface of the light guide GLB, and the light
source reflector LS is fixed on the upper side of the line light
source LP using the adhesive double coated tape BAT.
In the example shown in FIGS. 20A and 20B and FIGS. 21A and 21B,
the cold cathode fluorescent lamp LP constituting part of the
backlight BL is disposed along a long side of the liquid crystal
display module MDL under the display region. With this arrangement,
in the case where the LCD is mounted on an information processing
apparatus such as a personal computer or word processor as shown in
FIGS. 48 and 49, the cold cathode fluorescent lamp LP is located
under the long side of the display section of the processing
apparatus. In the example shown in FIGS. 15A to 15D in which the
inverter power source IV is disposed at the inverter housing
section MI in the display section, the lamp cable LPC1 is laid out
along two sides, left and upper sides of the liquid crystal display
module MDL and the lamp cable LPC2 is laid out along the right side
of the module MDL.
On the other hand, in the example shown in FIGS. 22A and 22B in
which the inverter power source IV is disposed in the key board,
the lamp cable LPC1 is laid out along three sides, left, upper and
right sides of the liquid crystal display module MDL and both the
lamp cables LPC1 and LPC2 extend from the lower right portion of
the module MDL.
The layout of the cold cathode fluorescent lamp LP under the
display section of the liquid crystal display module MDL is
advantageous in that even if the inverter power source IV is
disposed in the key board section as shown in FIG. 44, the length
of the high voltage side lamp cable LPC2 of the cold cathode
fluorescent lamp LP can be shortened, to reduce the impedance
causing noise and a change in waveform, thereby improving the
startability of the cold cathode fluorescent lamp LP. In addition,
by disposing the inverter power source IV on the key board side,
the width of the display section can be further reduced. The layout
of the cold cathode fluorescent lamp LP under the display section
is also effective to relax the shock due to opening/closing of the
display section, and hence to improve the reliability. Further, in
such a layout, since the center of the display screen of the liquid
crystal element PNL is shifted upwardly, there can be obtained an
effect of preventing the viewing to the lower portion of the
display screen from being obstructed by the operator's hands
operating the key board.
In the above configuration, the cold cathode fluorescent lamp LP is
disposed under the lower long side of the liquid crystal display
element PNL; however, it may be of course disposed over the upper
long side or outside each short side of the element PNL.
FIG. 42 is a block diagram illustrating the liquid crystal display
element PNL and the circuit configuration of driver circuits and
the like disposed at the outer peripheral portion of the liquid
crystal display element PNL, and FIG. 43 is a block diagram
illustrating the equivalent circuit of the liquid crystal display
module. In this configuration, the drain driver section 103 is
disposed only on the underside of the thin film transistor (TFT)
type liquid crystal display element PNL (TFT-LCD), and the gate
driver section 104, controller section 101 and power source 102 are
disposed on one side surface portion of the liquid crystal display
element (the number of picture elements: 800.times.600 pieces)
specified under the XGA Specification.
The drain driver section 103 is mounted on the above-described
multilayer flexible circuit board which is disposed in the folded
manner. The interface circuit board PCB on which the controller
section 101 and power source 102 are mounted is disposed on the
rear surface of the gate driver section 104 disposed at the outer
peripheral portion along the short side of the liquid crystal
display element PNL. The reason for this is that since the
information processing apparatus has a limitation in terms of the
lateral width, the lateral width of the liquid crystal display
module MDL constituting the display section of the processing
apparatus is also required to be made as small as possible.
As shown in FIG. 43, a thin film transistor TFT is disposed at an
intersection region formed by adjacent two drain signal lines DL
and adjacent two gate signal lines GL intersecting the two drain
signal lines. The drain electrode and gate electrode of the thin
film transistor TFT are connected to the associated drain signal
line DL and gate signal line GL, respectively.
The source electrode of the thin film transistor TFT is connected
to a picture element and the liquid crystal layer is provided
between the picture electrode and common electrode, so that a
liquid crystal capacitance (C.sub.LC) is connected between the
picture electrode and the source electrode of the thin film
transistor TFT. The thin film transistor TFT conducts when a
positive bias electrode is applied to the gate electrode, and it
does not conduct when a negative bias electrode is applied thereto.
A holding capacitance C.sub.add is connected between the source
electrode of the thin film transistor and the preceding gate signal
line.
It should be noted that in this LCD, since the polarity of the bias
voltage applied between the source and drain electrodes is inverted
during operation of the LCD, the source or drain electrode is
changed into the other depending on the inverted polarity of the
bias voltage during operation of the LCD. However, for convenience,
the following description will be made with one of the electrodes
taken fixedly as the source electrode and the other taken fixedly
as the drain electrode.
FIG. 44 is a diagram illustrating the flow of display data and
clock signals to the gate drivers and drain drivers.
FIG. 45 is a diagram showing the level and waveform of each of a
common electrode voltage, drain voltage, and gate voltage. The
drain waveform is that in the case of forming a black image.
FIG. 46 is a block diagram showing the schematic configuration of
each of the drivers (drain driver, gate driver, and common
electrode driver) for the liquid crystal display element and the
flow of signals thereamong. FIGS. 47A to 47D are timing charts
showing display data inputted from a host computer into a display
control device 201 and signals outputted from the display control
device 201 into the drain drivers and gate drivers.
The display control device 201 and a buffer circuit 210 are
provided in the controller section 101 shown in FIG. 42, and the
drain drivers 211 are provided in the drain driver section 103 and
the gate drivers 206 are provided in the gate driver section
104.
The drain driver 211 is composed of a data latch section for
display data and an output voltage generating circuit. A gradation
reference voltage generating section 208, a multiplexer 209, a
common-electrode voltage generating section 202, a common-electrode
driver 203, a level shift circuit 207, a gate-on voltage generating
section 204, a gate-off voltage generating section 205, and a
DC--DC converter 212 are provided in the power source 102 shown in
FIG. 42.
The display control device 201 is adapted to receive control
signals (clock signal, display timing signal, and synchronization
signal) from the host computer, and to create a clock signal D1
(CL1), a shift clock signal D2 (CL2), and display data as control
signals to the drain drivers 211 and simultaneously create a frame
start command signal FLM, a clock signal G (CL3), and display data
as control signals to the gate drivers 206.
The carry signal from the preceding stage of the drain driver 211
becomes the carry signal of the succeeding stage of the drain
driver 211.
As is apparent from FIGS. 47A to 47D, the shift clock signal D2
(CL2) for the drain drivers has a frequency identical to that of
each of the clock signal (DCLK) and display data inputted from the
host computer, which frequency is as high as about 40 MHz for the
display device under the XGA Specification. Accordingly, it becomes
important to take a measure against electromagnetic interference
(EMI).
Information Processing Apparatus on Which Liquid Crystal Display
Module is Mounted
FIGS. 48 and 49 are perspective views each showing a notebook type
personal computer or word processor on which the liquid crystal
display module MDL is mounted. As described above, FIG. 48 shows
the case in which the inverter power source IV is disposed in the
display section, that is, at the inverter housing section MI of the
liquid crystal display module MDL (see FIGS. 20A to 23E), and FIG.
49 shows the case in which the inverter power source IV is disposed
in the key board section.
Signal from the information processing apparatus are first supplied
to the integrated circuit device TCON for display control via a
connector positioned at an approximately central portion of the
interface circuit board PCB on the left side, to be subjected to
data conversion, and the display data flow in the peripheral
circuit for drain drives. Since the module MDL adopts the
chip-on-glass method and uses the multilayer flexible circuit board
as described above, it is possible to solve the limitation of the
information processing apparatus in terms of the lateral width and
outer shape thereof, and hence to realize the miniaturization and
low power consumption of the information processing apparatus.
Planar and Sectional Configurations of the Vicinity of Portion on
Which Driver IC Chips are Mounted
FIG. 31 is an enlarged view of an essential portion showing a state
in which the driver ICs are mounted on the lower substrate SUB1 of
the liquid crystal display element PNL, and FIG. 32 is a sectional
view taken on line 32--32 of FIG. 31. Referring to FIG. 31, the
upper substrate SUB2 designated by the chain line is superimposed
on the lower substrate SUB1 with a gap put therebetween, wherein a
useful display area AR is enclosed by means of a sealing pattern SL
and liquid crystal LC is injected in the enclosed area.
An electrode COM on the substrate SUB1 is a wiring electrically
connected to a common electrode pattern on the substrate SUB2 side
via conductive beads, paste or the like. Drain lines DTM or gate
lines GTM are adapted to supply output signals from the driver ICs
to interconnections in the useful display area AR. The input lines
Td are adapted to supply input signals into the driver ICs.
Anisotropic conductive films ACF include a strip-like ACF2 stuck
commonly to a plurality of the drivers IC portions arranged in a
row and a strip-like ACF1 stuck commonly to the input line pattern
portions connected to the plurality of the driver ICs.
Passivation films (protective films) PSV1 and PSV2 are, as shown
also in FIGS. 27A and 27B, formed in such a manner as to cover the
signal line portions as much as possible for preventing
electrolytic corrosion, and the exposed portions from the
passavation films are covered with the anisotropic conductive film
ACF1.
The peripheries around the side surfaces of the driver ICs are
filled with epoxy resin or silicone resin SIL (see FIG. 36) for
realizing multiple-protection.
Referring to FIG. 45, each of the gate-on level waveform (DC) and
gate-off level waveform is changed between -9 V to -14 V, with the
gate-on at 10 V. Each of the drain waveform (upon black display)
and common-electrode voltage (V.sub.com) waveform is changed in its
level between about 0 V to 3 V. For example, to change the drain
waveform (black display) for each horizontal scan period (1H),
logical inversion is performed for one bit by the logical circuit
to input the drain waveform to the drain drivers. The gate-off
level waveworm is changed at an amplitude and phase which are
substantially the same as those of the common-voltage (V.sub.com)
waveform.
FIG. 44 is a diagram illustrating the flow of display data and
clock signals to the gate drivers 104 and drain drivers 103. As
described above, the display control device 101 is adapted to
receive control signals (clock signal, display timing signal, and
synchronization signal) from the host computer, and to create a
clock signal D1 (CL1), a shift clock signal D2 (CL2), and display
data as control signals to the drain drivers 103 and simultaneously
create a frame start command signal FLM, a clock signal G (CL3),
and display data as control signals to the gate drivers 104.
The carry signal from the preceding stage of the drain driver 103
becomes the carry signal of the succeeding stage of the drain
driver 103.
While the embodiments of the present invention have been described
in detail, the present invention is not limited thereto, but many
changes may be made without departing from the scope of the present
invention. For example, in the above embodiments, the present
invention is applied to the active matrix type liquid crystal
display device; however, the present invention can be applied to
liquid crystal display devices of other types such as a simple
matrix type. Further, the present invention can be applied not only
to the flip-chip method in which driver ICs are directly mounted on
a substrate but to the conventional method using the TCP.
As described above, according to the present invention, the
reduction in frame border area of a liquid crystal display device
can be realized by adopting the electrically connecting structure
between the flexible circuit board and upper case, the structure of
holding the liquid crystal display element and light guide while
ensuring a high resistance against shock, and the crimp-clamping
structure of the upper and lower cases.
* * * * *